It used to be that Astronomy was distinct from physics (e.g. back in the days of Ptolemy and Aristotle). One would have various models of the universe, or various observations of the universe and these would have nothing to do with Physics. As modern Astronomy developed, people found that we could use the laws of physics to describe what's happening in the sky too (e.g. Newton's Universal Law of Gravitation). Now, the two are quite inseparable, and we call it Astrophysics.

Astronomy is what grad and post doctoral students do to live in a 2 bedroom flat with 3 other people and eat ramen noodles. They gather the observational evidence used by astrophysicists to cipher the nature of the universe - IOW, what nick said.